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Or the algae in the sea ? Or the cacti in the desserts ? How does trees on the fertile plain obtain their nutrients ?

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Presentation on theme: "Or the algae in the sea ? Or the cacti in the desserts ? How does trees on the fertile plain obtain their nutrients ?"— Presentation transcript:

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3 Or the algae in the sea ? Or the cacti in the desserts ? How does trees on the fertile plain obtain their nutrients ?

4 Review Question Which mode of nutrition do the green plants carry out? A.Autotrophic nutrition B.Heterotrophic nutrition

5 Sorry! You’re wrong! Heterotrophic nutrition is the mode of nutrition in which organisms have to depend on other organisms or dead organic matters as their food sources. Green plants, however, can make organic food by themselves using simple inorganic substances.

6 Very Good! Autotrophic nutrition is the mode of nutrition in which organisms can make organic food by themselves using simple inorganic substances. The process by which the green plants obtain nutrients is called : Photosynthesis

7 Nature of photosynthesis Takes place in Chloroplast Necessary factors :   Carbon dioxide   Water   Sunlight   Chlorophyll

8 Route of Carbon Dioxide for Photosynthesis

9 CO 2 Stoma Air Space Spongy Mesophyll Cell Chloroplast

10 CO 2 Chloroplast Palisade Mesophyll Cell Stoma Air Space

11  Light energy is trapped by chlorophyll in chloroplast  Light energy absorbed by chlorophyll splits water molecules into hydrogen and oxygen  Oxygen is released as a gas through stoma to outside  Hydrogen is fed into dark reaction Light reaction

12 bluered % of light absorbed by chlorophyll green 6

13 Oxygen is produce as the by-product of photosynthesis.

14 Dark reaction  No light is required; can take place either in light or darkness  Hydrogen produced in light reaction combines with CO 2 to form carbohydrates  Water is formed as a by-product

15 Dark Reaction Water Oxygen Glucose (C 6 H 12 O 6 ) Light Reaction H Summary of Photosynthesis 6 CO 2 + 6 H 2 0 C 6 H 12 O 6 + 6 O 2 Light Carbon Dioxide

16 Fate of carbohydrate products in the plant

17 carbohydrates (e.g. glucose) carbon dioxide and water photosynthesis release energy by respiration

18 convert into starch for storage because glucose is not a very good storage molecule carbohydrates (e.g. glucose) carbon dioxide and water photosynthesis

19 change into sucrose and is transported to other parts through phloem carbohydrates (e.g. glucose) carbon dioxide and water photosynthesis

20 carbon dioxide and water photosynthesis carbohydrates (e.g. glucose) fatty acidsglycerol combine to form fats and oils to form cell membranes and as a food store

21 carbon dioxide and water photosynthesis carbohydrates (e.g. glucose) mineral salts from soil (e.g. NO 3 -, SO 4 2- ) amino acids join together to become protein molecules

22 Experiments on photosynthesis

23 Destarching Reason: –To avoid any existing starch in the leaves interfering with the result, and to show that any starch found after the experiment is produced during the period of investigation Method: –By placing the plant in dark for at least 48 hours

24 To test a leaf for the presence of Starch

25 Why is the leaf first boiled in water ? Ans: Because the process can soften the leaf, break down the cuticle and kill the leaf. boiling water turn off Bunsen burner boiling alcohol hot water iodine white tile turn off Bunsen burner

26 Why is the leaf then boiled in alcohol ? Ans: To decolourize the leaf (to remove chlorophyll). boiling water turn off Bunsen burner boiling alcohol hot water iodine white tile turn off Bunsen burner

27 Why is it important to turn off the Bunsen burner when you are heating the alcohol ? Ans: Because alcohol catches fire easily. boiling water turn off Bunsen burner boiling alcohol hot water iodine white tile turn off Bunsen burner

28 Why is the leaf put in hot water after being boiled in alcohol ? Ans: Since the leaf becomes brittle after boiling in alcohol, so dipping it into hot water enables it to be softened. boiling water turn off Bunsen burner boiling alcohol hot water iodine white tile turn off Bunsen burner

29 What colour change can be observed if starch is present ? Ans: The leaf becomes blue-black when iodine solution is added to it. boiling water turn off Bunsen burner boiling alcohol hot water iodine white tile turn off Bunsen burner

30 To show that Chlorophyll is necessary for Photosynthesis

31 Which part of the leaf turns blue-black when treated with iodine solution ? Ans: Only the green part. green part purple part

32 Is chlorophyll necessary for photosynthesis ? Ans: Yes. green part purple part

33 What is the control in this experiment ? Ans: The green part of the leaf acts as the control. green part purple part

34 To show that Carbon Dioxide is necessary for Photosynthesis

35 Why is potassium hydroxide solution put in one of the flasks ? Ans: To absorb all the carbon dioxide in flask B. sunlight B A water potassium hydroxide solution

36 What happens to each leaf after testing the presence of starch at the end of the experiment ? Ans: The leaf in flask A changes to blue-black while the leaf in flask B stains brown. sunlight B A water potassium hydroxide solution

37 What do your results suggest about the relationship between carbon dioxide and photosynthesis ? Ans: Carbon dioxide is necessary for photosynthesis. sunlight B A water potassium hydroxide solution

38 Factors affecting the rate of photosynthesis

39  Light intensity  Rate of Photosynthesis

40  Carbon dioxide concentration  Rate of Photosynthesis

41  Temperature  Rate of Photosynthesis Temperature > 40 ℃ Rate  & Stop soon

42 If no water, stomata close no gaseous exchange photosynthesis ceases

43 Why is Photosynthesis important ? Green plants: the only organisms capable of trapping light to manufacture food from simple inorganic substances

44 Green plants(producers) starts the food chain & provide food for other organisms Why is Photosynthesis important ?

45 Atmospheric carbon dioxide is absorbed & oxygen is released into the atmosphere which maintains the composition of the atmosphere constant Why is Photosynthesis important ?

46 Parts of plant where photosynthesis takes place Mainly in the leaf because –it contains a lot of chloroplasts –it is well adapted for performing photosynthesis

47 Internal Structure of Leaf

48 cuticle upper epidermis palisade mesophyll spongy mesophyll intercellular space (air space) guard cell lower epidermis cuticle stoma chloroplasts

49 Cross-section of a leaf of dicotyledon

50 upper epidermis protect internal tissues from mechanical damage and bacterial & fungal invasion

51 Cuticle a waxy layer prevent water loss from the leaf surface protect the leaf

52 mesophyll

53 palisade mesophyll (layer) columnar cells closely packed together  absorb light more efficiently contains many chloroplasts

54 spongy mesophyll (layer) irregular cells loosely packed together to leave numerous large air spaces  allow rapid diffusion of gases throughout the leaf some (fewer than palisade mesophyll) chloroplasts for photosynthesis

55 lower epidermis same as upper epidermis except the cuticle is thinner

56 stoma (stomata) opening which allows gases to pass through it to go into or out of the leaf

57 guard cells control the size of stoma

58 Stoma stoma Guard cells thinner outer wall thicker inner wall

59 vascular bundle (vein)

60 Internal Structure of Leaf xylem phloem

61 xylem to transport water and mineral salts towards the leaf for mechanical support

62 phloem to transport organic substances (food/sugar/ glucose/ sucrose) away from the leaf

63 Adaptation of leaf to photosynthesis

64 The leaf is thin decrease diffusion distance for gases & light The leaf is broad & flattened increase surface area to absorb more sunlight

65 Cuticle exists in upper epidermis and is transparent Allows most light to pass into photosynthetic mesophyll tissues

66 Palisade mesophyll cells are closely packed and contain many chloroplasts To carry out photosynthesis more efficiently

67 Spongy mesophyll cells are loosely packed with numerous large air spaces To allow rapid diffusion of gases throughout the leaf

68 Numerous stomata on lower epidermis To allow rapid gaseous exchange with the atmosphere

69 Extensive vein system Allow sufficient water to reach the cells in the leaf To carry food away to other parts of the plant

70 Mineral requirements in plants In order to synthesize amino acids, nitrate ions which must be taken into the plant from the soil through the root Other minerals are also necessary to maintain the life of the plant (N, Mg, P, K, S, etc)

71 The importance of nitrogen For synthesis of proteins, chlorophyll, etc Taken in form of nitrate ions Deficiency symptoms: –Little growth ( - no protein made) –Yellowing of leaves ( - no chlorophyll made)

72 The importance of magnesium Essential component of chlorophyll Deficiency symptoms: –Yellowing of leaves (no chlorophyll made) –Poor growth (no food manufactured because of lack of chlorophyll)

73 Use of fertilizers in agriculture Continuous harvesting crops removes valuable mineral salts from soil  Fertilizers are added to replace such loss Two kinds of fertilizers: –Natural fertilizers –Chemical fertilizers

74 Natural fertilizers From manure Organic compounds in it are decomposed by the bacteria in soil to form mineral salts

75 Chemical fertilizers Mainly nitrogenous and phosphorous compounds manufactured artificially

76 Comparison between natural and chemical fertilizers Natural fertilizersChemical fertilizers Contain humus which can improve soil texture No humus so cannot improve soil texture Less soluble in water so less likely to be washed away Very soluble in water so more likely to be washed away

77 Comparison between natural and chemical fertilizers Natural fertilizersChemical fertilizers Less soluble in water so more difficult to be absorbed Very soluble in water so easier to be absorbed More readily to be used by the plants Time is needed for the decomposition to complete before nutrients are available to plants Very expensiveMuch cheaper

78 ~ END ~ ~ END ~


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